Inverters are known in which a bridge (e.g. an H bridge) is adapted to chop a voltage from a direct voltage source for feeding an alternating voltage to a primary of a transformer; the inverter further comprises a diode rectifier-leveler circuit receiving the input alternating voltage from the secondary of the transformer in order to achieve a leveled voltage fed to a chopper which in turn feeds a load. The chopper generally includes a plurality of parallel branches (different chopper structures with two, three or more stages are possible), each of which consists of a pair of electronic semiconductor switches arranged in series and interposed between a positive power supply line and a negative power supply line from the rectifier-leveler circuit. The common terminals of the electronic switches of the chopper communicate with load power supply lines; each electronic switch of the chopper is also provided with a recirculation diode arranged in parallel.
The switching of the electronic switches of the chopper is controlled by an electronic unit which operates a certain load feeding program (for example, if such a load is an electric motor, the rotation speed of the motor and the power delivered by the motor itself can be set and adjusted).
Known electronic units control the switching of the chopper switches, under many operating conditions, in the presence of voltage at the ends of the switches themselves; such an operation—as known from the physics Of semiconductors—results in a power dissipation that contributes to a considerable part of switching losses.